In the field of synchronous motors, a rotor as mentioned above, which includes permanent magnets magnetized in a circumferential direction and laminated core members each forming a magnetic pole between the permanent magnets, the magnets and the core members being alternately disposed around a shaft, has been used. In this type of conventional rotor, each laminated core member is generally formed by stacking a plurality of core-laminations made of magnetic materials such as silicon steel plates. Each core-lamination may have recesses and projections, which are formed at corresponding positions on respective axial end faces of core-lamination and can be engaged with each other. The core-laminations can be joined to each other by, e.g., press-fitting the core-laminations together while aligning the recesses and projections of the adjacent core-laminations. Each permanent magnet is held between a pair of adjacent laminated core members and brought into close contact with the side faces of the latter. The permanent magnet may be positioned and fixedly supported in a radial direction by outer and inner hooks protruding from the side faces of each laminated core member at outer and inner peripheral regions thereof. A rod member may be inserted into an axial through hole formed generally at the center of each laminated core member. Each rod member may be connected to annular end plates which are arranged at both axial ends of the laminated core member and fixed to the rotating shaft. In this manner, the laminated core members and the permanent magnets are fixedly held in the rotor against external force such as centrifugal force, by the end plates, the rod members and the hooks.
This type of rotor uses a plurality of permanent magnets and laminated core members, the number of which corresponds to the number of magnetic poles, therefore it has problems in that the work of positioning or fixing the permanent magnets and laminated core members is complicated, increased working time and skilled workers are required, and thus improvement of personnel requirements and productivity is prevented. Further, the accuracy of positioning the permanent magnets and laminated core members depends on the mechanical strength and processing accuracy of the rod members and end plates. Consequently, in the case of high speed motors or high torque motors, additional means for improving the mechanical strength of the whole structure of the rotor is required in order to accurately hold the permanent magnets and laminated core members in predetermined positions.